a) Field of the Invention
The invention is directed to an arrangement for the illumination of a field which uses, as light source, three groups of LEDs which emit light bundles (100) of different colors (red, green, blue), wherein the light bundles—considered in the direction of light propagation—pass collector optics, a device for combining the light bundles, and in-coupling optics. The arrangement is applied particularly as an illumination module in projectors. The field in question is identical to the light inlet face of a light mixing rod. Another application, for example, is the illumination of objects in microscopes.
b) Description of the Related Art
DE 103 41 626 A1 discloses an illumination module for displaying color images which uses three LEDs or LED arrays as light source. The light components in the three primary colors, red, green and blue, are coupled into a light inlet face of a light mixing rod via dichroid filters. Refractive lenses are used for beam shaping to couple the light emitted by the LEDs into the light inlet face of the light mixing rod. This reference shows that identical optics are used for an LED and for an LED array. While an individual LED can be regarded in a first approximation as a point light source, the geometric-optical ratios in an LED array are fundamentally different, which should be taken into account in the design of the optical arrangement, especially when the aim is to couple the light emitted by the LED array into the light mixing rod as completely as possible.